At the top of the options is Clear All which clears all formatting and styles from a document.
To quickly remove styles, expand Quick Styles to display the list of available styles. You can also select just a few paragraphs and use the same method to remove formatting from part of a document. Use Ctrl + A to select all text in a document and then click the Clear All Formatting button to remove the formatting from the text (aka character level formatting.) Pro Tip - If you are struggling for more than a few minutes with formatting, it is usually best just to clear out the old formatting and then properly format the resulting clean document. If you use Microsoft Word, you have almost certainly struggled with Word formatting issues, especially using Word documents created by others and edited by many people.